Podcast
Questions and Answers
What is the purpose of React.Fragment in React?
What is the purpose of React.Fragment in React?
- To create a reusable component
- To group multiple children elements without adding extra nodes to the DOM (correct)
- To define a new context for child components
- To handle form inputs
In React, what is the purpose of the key prop when rendering a list of components?
In React, what is the purpose of the key prop when rendering a list of components?
- It is used to uniquely identify each child element in a list (correct)
- It specifies the styling for each child element
- It defines the structure of the child components
- It determines the order in which the elements are rendered
What is the purpose of React.memo in React functional components?
What is the purpose of React.memo in React functional components?
- To memoize the component's state
- To memoize the component's props
- To memoize the component's context
- To memoize the component's rendering (correct)
In React, when should you use a controlled component instead of an uncontrolled component?
In React, when should you use a controlled component instead of an uncontrolled component?
How does React optimize rendering performance when updating the DOM?
How does React optimize rendering performance when updating the DOM?
What is the purpose of the useReducer hook in React?
What is the purpose of the useReducer hook in React?
What will be logged to the console when the following code is executed? const a = { key: 'value' }; const b = a; b.key = 'updated value'; console.log(a.key);
What will be logged to the console when the following code is executed? const a = { key: 'value' }; const b = a; b.key = 'updated value'; console.log(a.key);
Which of the following is true about JavaScript's Promise.allSettled() method?
Which of the following is true about JavaScript's Promise.allSettled() method?
What does the Symbol datatype represent in JavaScript?
What does the Symbol datatype represent in JavaScript?
When using the await keyword within an async function in JavaScript, which of the following is true?
When using the await keyword within an async function in JavaScript, which of the following is true?
What will be the output of the following code? const value = Promise.resolve(5); console.log(typeof value);
What will be the output of the following code? const value = Promise.resolve(5); console.log(typeof value);
In React, which lifecycle method is invoked immediately after a component is inserted into the DOM?
In React, which lifecycle method is invoked immediately after a component is inserted into the DOM?
Study Notes
React Lifecycle Methods
componentDidMount()is invoked immediately after a component is inserted into the DOM
React.Fragment
- Purpose: to group multiple children elements without adding extra nodes to the DOM
React Key Prop
- Purpose: to uniquely identify each child element in a list when rendering a list of components
React.memo
- Purpose: to memoize the component's props in functional components
Preventing Component Rerender
- Use
shouldComponentUpdatelifecycle method orReact.memoto prevent a React component from rerendering when its parent re-renders
Controlled vs Uncontrolled Components
- Use controlled components when the input value is controlled by React state or when the form is dynamic
React Hooks
- Allow you to use state and other React features without writing a class
- Can be used for managing state, handling side effects, and more
React Rendering Optimization
- React optimizes rendering performance by using a virtual DOM
useEffect Hook
- Purpose: to perform side effects in function components
useReducer Hook
- Purpose: to manage complex state logic in a cleaner way
JavaScript Objects and References
- When you update a copied object, the original object is also updated because objects are references
JavaScript Promises
Promise.allSettled()waits for all promises to be either resolved or rejected
JavaScript Symbol Datatype
- Represents unique and immutable values
Async/Await in JavaScript
- When using the
awaitkeyword, the async function waits for the awaited promise to resolve or reject
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Description
Test your knowledge on JavaScript object reference and the Promise.allSettled() method. Determine what will be logged to the console in a given code snippet, and understand the behavior of Promise.allSettled().
